Soluble cutting oil and method of applying the same



SOLUBLE CUTTING OIL AND METHOD OF APPLYING THE SAME Henry A. Ambrose, Penn Township, Allegheny County, and Joseph H. Piatt, Plum Township, Allegheny County, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application December 16, 1953 Serial No. 398,636

3 Claims. (Cl. 252-334) This invention relates to cutting liquids employed in' metal working operations and more particularly to soluble cutting oils which are adapted to be directed as a thin, high speed jet into the angle between the work and the cutting edge of the tool.

The application of a cutting oil to a meta surface being worked has conventionally comprised flowing over the metal working tool, either by gravity or under low pressure, a large amount of the oil, the theory being that by flooding the working surface with the cutting oil the heat evolved in the operation would be dissipated, the

metal chips washed away and the cutting operation lubricated by the large quantity of oil used. However, in the cutting operation the chip which is formed overlies and shields the cutting edge so that an insufficient amount,

if any, of the cutting oil flooding the work from overhead scribed in the patent of R. J. S. Pigott, U. S. 2,653,517.

In the new method a thin, high speed jet of oil is directed between the work and the cutting surface of the tool. A velocity of the jet such as 225 to 260 feet per second is obtained by pumping the oil at pressures such as 300 to 600 pounds per square inch through a small nozzle. As a result, it is believed that at least a portion of the oil, possibly as a vapor which thereafter condenses, penetrates the very small clearance between the work and the relief surface of the tool without impinging upon the heel of the tool or otherwise dissipating its energy before reaching its destination. In this manner the cutting operation is more efficiently cooled and lubricated so that the life of the cutting tool is increased, build-up of metal particles on the cutting tool is reduced or eliminated, the surface of the finished work is improved and other important advantages are obtained.

While the newly developed technique of applying the cutting liquid to the work as a high speed jet results in increased tool life even with cutting liquids of conventional composition, the conventional cutting liquids have not proven to be entirely satisfactory for the new technique. A serious problem encountered in the use of conventional cutting oils in the high speed jet technique has been the formation of large amounts of smoke or vapor during the cutting operation. Conventional soluble cutting oils which reduce the smoking problem are not entirely satisfactory with respect to the'increased tool life which should result from the use of the high Patented July 1, 1958 speed jet technique. An objectof the present invention is to increase further the advantages. obtainable through the high speed jet method of applying cutting liquids by providing cutting liquids which are particularly adapted for the newly developedmethod of application.

In accordance with the present invention, we have produced a soluble cutting oil which is particularly adapted to be employed in an emulsion with water in metal working operations in which the cutting liquid is directed 'at a high velocity between the tool and the Work as a thin, high speed jet and which comprises a lubricating oil having a Saybolt Universal viscosity greater than 210 seconds at 210 F. and an emulsifying agent. Our invention also in general comprises an improvement in the method of working metal in which a thin, high speed jet of cutting liquid is directed at a high velocity between the tool and the work, the improvement comprising the use of a cutting liquid composed of water and a soluble cutting oil of the described composition.

' such as, for example, a lubricating oil obtained by Fischer- Tropsch synthesis, by olefin polymerization, etc. The maximum viscosity permissible for the heavy oils em- 'ployed in our compositions is not a critical factor although, in general, heavy oils-having a viscosity no greater 'than'about 1,000 SUS at 210 F. are preferred.

A high viscosity mineral lubricating oil which is particularly advantageous for producing the compositions of our invention is a heavy neutral oil having the inspection data listed in Table I below.

Table I Gravity, API' 25.9 at 210 F.

Viscosity, SUS:

At 100 F 66,708 At 210 F 523 Flash point, F 550 51 Fire point, F 670 Pour point, F Color, NPA 6 dilute Carbon residue percent 3.35 Sulfur do 1.58 Ash do 0.01

Another high viscosity mineral oil which has been used advantageously in our compositions is a heavy Pennsylvania oil stock having the inspection data listed in Table II.

Table II p Gravity, API 21.8 Viscosity, SUS:

At F 36,050

At F 9,443

At 210 F 868 Color, NPA 3 /2 Pour point, F .|50

Neutralization No 0.22

Saponification No -L 1.3

Flash point, F 690 'Fire point, F 740 Still another heavy mineral lubricating oil used with advantage in our compositions is a Mid-Continent reduced, centrifuged, solvent processed oil having the inspection data listed in Table III.

3 Table III Gravity, API 22.6 Sp. Gr. 60/60 F 0.9088 Viscosity, SUS:

At 100 F 4286 At 130 F"; 1511 At 210 F 216 Viscosity Index 98 Flash point, "F 625 Fire point, F 695 Neutralization No 0.16 Saponification No 0.9 Sulfur percent 0.25 Ash as oxide do 0.02

Particularly suitable oil-in-water emulsifying agents for use in the soluble oil compositions of our invention are oil-soluble sulfonates such as the mahogany sulfonates formed in the sulfonation of petroleum oils. They are ordinarily prepared as alkali metal sulfonates, for ex- H ample, as sodium mahogany sulfonates. Either the purified sulfonates or any of the commercial mahogany sulfonates of varying grades of purity can be used. Numerous other conventional oil-in-water emulsifying agents can be used including sulfonated fatty material such as sperm oil, olive oil, cottonseed oil, etc. Also suitable are emulsifying agents such as the stearates and oleates of alkylolamines such as mono-, di-, or triethanol amine and non-ionic'complex esters such as polyoxyethylene sorbitan fatty acid esters.

The relative amounts of viscous lubricating oil and emulsifying agent in the soluble oil will depend upon the ease with which the oil is made emulsifiable and upon the efliciency of the particular emulsifying agent. Usually, the emulsifying agent will comprise from about to 40 percent by weight of the soluble oil composition. However, with easily emulsifiable oils as little as 5 weight percent of the emulsifying agent may sufiice while with difiicultly emulsifiable oils it may be necessary that the soluble oil comprise as much as weight percent emulsifying agent..

In preparing stable emulsions of oil and water with emulsifying agents of the types indicated, it is often desirable to adjust the pH of the mixture by the addition of acid or basic substances. Therefore, the soluble oil compositions of our invention can contain minor amounts of materials such as oleic acid or caustic, added for the purpose of adjusting the pH of the mixture and affording the maximum stability of the emulsion. Our compositions may also contain a minor amount of a suitable coupling agent such as diethylene glycol to improve the emulsion stability.

In addition to the high viscosity oil base, the emulsifying agent, any acid or basic material necessary for pH adjustment, and any desired coupling agent, the soluble oils of our invention may include various agents such as rust inhibitors, extreme pressure agents, antiseptics, etc. I

The preparation of the soluble oils of our invention requires merely that the mixture of ingredients, i. e., the heavy oil, the emulsifying agent, and any desired additives be stirred until a clear mixture is obtained. Usually, warming the mixture to a temperature of from about 100 to 120 F. in the preparation is advisable. Finally, the maximum emulsifiability of the composition can be obtained by adjusting the pH as by the addition of minor amounts of acid or base until the mixture is easily emulsifiable.

The'cutting liquid compositions or emulsions of our invention can vary considerably in the ratio of the amount of water to the amount of soluble oil depend- 7 ing upon a number of factors such as the emulsifiability of the particular soluble oil, the proportion of oilre- A quired to lubricate properly the cutting operation, the

smoking problem at high oil concentrations, etc. For

iii)

most cutting operations the cutting liquid should contain at least about 5 percent of the soluble oil and usually at compositions above about 20 percent by volume of soluble oil the smoking problem begins to be serious. Therefore, from about 5 to 20 percent by volume of the soluble oil is the preferred range of composition in the emulsion. However, in certain operations and with certain soluble oil compositions of our invention, as little as from 1 to 2 percent emulsions may be employed and in other operations as much as 50 percent by volume emulsions may be employed.

We have conducted lathe tests with cutting liquids of our invention and with a conventional cutting liquid which show the increased tool life made possible by using the cutting liquids of our invention in the high speed jet-technique. Three different soluble cutting oil compositions of our invention were prepared using the high viscosity mineral oils of Tables I, II and III above. The compositions were as follows:

Composition A: Weight percent Heavy oil of Table I 68.5

Sodium petroleum sulfonate 30.0 Oleic acid (commercial) 1.5

Composition B:

Heavy Pennsylvania stock of Table ii 71.0 Sodium petroleum sulfonate 25.0 Qleic acid {commercial} 4.0 Composition C: Weight percent Mid-Continent heavy oil of Table III 66.0 Sodium petroleum sulfonate 30.0 Oleic acid (commercial) 4.0

A conventional soluble cutting oil prepared from a light mineral oil was also employed in the lathe tests. The oil base of the conventional soluble cutting oil was a 100/ 2 Texas oil having the inspection data listed in Table IV.

The conventional soluble cutting oil had the following composition 2 Composition D: Weight percent 100/2 Texas oil of Table IV 85.00 Sodium petroleum sulfonate 14.88 Rust inhibiting agent (alkylamine isoamyl octyl orthophosphate) 0.12

Each of the soluble oil compositions A, B, C and D were mixed with water to form cutting liquid emulsions comprising 5 percent by volume of the soluble oil. The cutting liquids were subjected to lathe tests on AISI 4140 mill annealed steel using a high speed steel tool (shape:

' 1012 1066-'i%4" R). in these tests the cutting liquids were directed in the form of a thin jet at a velocity of about 246 feet per second and about 0.125 gallons per minute into the angle between the work and the tool. The thin jet was obtained by passing the cutting liquid through a small 'orifice (0.0183 inch) in a nozzle which was mounted on the carriage of the lathe. The cutting liquids were supplied to the nozzle at a temperature of about to F. under a pressure of about 400 pounds per square inch. The depth of cut was 0.088

inch and the feed was 0.011 inch per revolution. The results of the lathe tests in terms of actual tool life and adjusted tool life (derived in the manner hereinafter described) are given in Table V.

Table V.Tol life tests of soluble cutting oils [In 6 vol. percent emulsions with water.]

1 S. F. M.=Surface feet per minute.

In lathe tests such as those described above, a problem arises in interpreting the tool life results due to unavoidable difierences in the machineability of the various steel specimens. Consequently, it is desirable to adjust the test results for the differences in the steel specimens where possible. A method of adjusting the results is by the calculation of adjusted tool life values such as those presented in Table V above. These are obtained as follows: For a particular steel a large number of determinations of the dry tool life of different specimens of the steel are taken and an average value is calculated. For the A181 4140 steel of these tests, at a speed of 140 SFM a dry life value of approximately 1.4 minutes was obtained. This factor which is in effect a machineability rating of the steel, is then used in the following formula to obtain the adjusted tool life for a specimen of this particular steel at any cutting speed.

dry tool life at 140 SFM for the particular steel specimen being used and of the tool life with the cutting liquid being Adjusted tool life= tested. The adjusted tool life which can then be obtained by the formula furnishes a reliable basis for comparing the efliciency of the various cutting oils by compensating for the machineability of the particular steel specimen. In Table V above, the adjusted tool life values are given as the average of adjusted tool life values for the tests made at the same cutting speeds.

The results of the tests recorded in Table V show markedly increased tool life for the cutting liquids of our invention as compared with the conventional cutting liquid. The superiority is shown in the actual tool life values as well as the adjusted tool life values and at both cutting speeds employed in the tests. As the data show, at the cutting speeds of and SFM the actual and adjusted tool life values, when the cutting compositions of our invention were employed, were two or three times greater than'when the conventional cutting composition was employed.

Although the cutting liquid compositions of the invention are particularly adapted for application as a thin, high speed jet, as described herein, it should be understood that they are also useful and have important advantages when applied as cutting liquids by other methods, for example, by the conventional overhead method of application.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the method of working metal in which a thin, high speed jet of cutting liquid is directed at a high velocity between the tool and the work, the improvement which'comprises using as the cutting liquid an emulsion comprising a major amount of water and a minor amount of an emulsifiable cutting oil comprising from about 50 to 95 percent by weight of a mineral lubricating oil having a Saybolt Universal viscosity at 210 F. greater than 210 seconds and from about 5 to 50 percent by weight of an emulsifying agent.

2. In the method of working metal in which a thin, high speed jet of cutting liquid is directed at a high velocity between the tool and the work, the improvement which comprises using as the cutting liquid an emulsion comprising a major amount of water and from about 5 to 20 volume percent of an emulsifiable cutting oil comprising from about 50 to 95 percent by weight of a mineral lubricating oil having a Saybolt Universal viscosity at-210 F. between about 210 and 1,000 seconds and from about 5 to 50 percent by weight of an oil-soluble sulfonate emulsifying agent.

3. The method of claim 2 in which said emulsifying agent is a sodium mahogany sulfonate.

References Cited in the file of this patent UNITED STATES PATENTS Adams et al. May 5, 1936 Pigott Sept. 29, 1953 OTHER REFERENCES New York, N. Y., 1951, page 311. 

1. IN THE METHOD OF WORKING METAL IN WHICH A THIN, HIGH SPEED JET OF CUTTING LIQUID IS DIRECTED AT A HIGH VELOCITY BETWEEN THE TOOL AND THE WORK, THE IMPROVEMENT WHICH COMPRISES USING AS THE CUTTING LIQUID AN EMULSION COMPRISING A MAJOR AMOUNT OF WATER AND A MINOR AMOUNT OF AN EMULSIFIABLE CUTTING OIL COMPRISING FROM ABOUT 50 TO 95 PERCENT BY WEIGHT OF A MINERAL LUBRICATING OIL HAVING A SAYBOLT UNIVERSAL AT 210*F. GREATER THAN 210 SECONDS AND FROM 5 TO 50 PERCENT BY WEIGHT OF AN EMULSIFYING AGENT. 